Not Applicable
1. Field of the Invention
This invention is in the field of retrieving stuck tools which are suspended downhole in an oil or gas well on a wireline.
2. Background Art
During the drilling of an oil or gas well, tools called well logging tools are often run into the well bore suspended on a wireline. These tools can be used for such purposes as measuring various properties of the earth formation at selected depths. While suspended in the well bore, such tools sometimes become stuck, either in an open hole portion of the well bore, or even in a cased portion. It then becomes necessary to retrieve the stuck tool from the well bore. In open hole, this is usually done by cutting the wireline at the earth""s surface, then running a drill pipe into the well over the wireline. An attachment tool, such as a grappling tool, on the lower end of the drill string is attached to the stuck tool. Then, the wireline is pulled until it separates from the cable head on the stuck tool, and the downhole tool is then retrieved with the drill string. In cased hole, the wireline is normally pulled out of the cable head first, then the stuck tool is fished out, either with a wireline fishing tool or a tubing conveyed fishing tool.
The retrieval operation is sometimes further complicated by an unplanned separation of the wireline some distance above the tool, rather than at the cable head, leaving some portion of the wireline in the well, suspended above or lying on top of the stuck tool. This unplanned separation of the wireline can also occur when the wireline is pulled in order to loosen or retrieve a stuck tool.
Unplanned separation of the wireline can be minimized by including a weak point in the string, just above the suspended tool. This insures that the wireline will break at this weak point, allowing all of the wireline to be retrieved from the well bore before fishing or retrieval of the stuck tool is attempted. Unfortunately, the use of a weak point limits the weight of the tool string that can be suspended from a wireline, as well as the amount of pull the operator can apply in order to free a stuck tool.
Unplanned separation of the wireline can also be minimized by including an explosive driven wireline cutter above the downhole tool. Such tools suffer from the disadvantage that they must be installed in the wireline before running in the tool, and they require a separate fishing operation after the wireline is severed. Explosively severing the wireline can also loosen the attachment between a grappling tool and the stuck tool.
Even when the retrieval operation goes without complications, since the wireline is severed before unsticking the tool, the stuck tool must be completely removed from the well bore, then a new or reconnected tool run back into the well to complete the logging operation which was originally underway.
It would be beneficial, then, to have a combination tool which can attach to a stuck tool, loosen the stuck tool, sever the wireline just above the tool allowing retrieval of the wireline, and then retrieve the tool. It would also be beneficial to be able to attach to the stuck tool, loosen and reposition the tool for completion of its original operation, and then have the ability to sever the wireline if necessary, all with a single tool.
The present invention is a combination tool including an attachment tool such as a grapple, and a hydraulically driven wireline cutter, both mounted on a tubular work string. The work string is lowered into the well bore over the wireline, and the grapple is attached to the stuck tool. The work string can be raised and lowered slightly, to confirm the attachment. Fluid flow is then increased to drive a piston and wedge, which in turn drives a cutter blade through the wireline, severing it just above the stuck tool. The entire length of the wireline can then be pulled from the well, after which the work string is used to loosen and retrieve the stuck tool.
Alternatively, after the grapple is attached to the stuck tool, the wireline can be cut at the well site on the earth surface and routed through a side door in the work string, and reconnected. Then, the work string can be used to loosen the stuck tool and reposition it downhole as required for the completion of the originally planned operation of the tool, such as well logging operations. Then, the entire assembly can be retrieved with the work string, or the wireline can be hydraulically severed at the stuck tool and retrieved, followed by retrieval of the stuck tool itself.
The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: